Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
1998-09-30
2001-01-30
Lam, Tuan T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S139000, C327S538000
Reexamination Certificate
active
06181171
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a circuit configuration for pulsed current regulation of inductive loads, including a switching device connected in series with the inductive load between two supply-voltage terminals, and a measuring device for recording a signal corresponding to a current through the inductive load.
In order to provide for pulsed current regulation of inductive loads, as is customary, for example, for speed regulation of DC motors or for switched-mode power supplies, it is often necessary to measure the amplitude of the current through the inductive load and to use that measurement to set the duty ratio of the current regulation. An example of such pulsed current regulation has been described in German Utility Model G 91 05 697.7 U1, which is assigned to the assignee of the instant application. The switched-mode power supply described in that publication has a power MOSFET which is disposed in series with a primary winding of a transformer and has a so-called shunt resistor connected in series with it toward ground. A voltage drop across that resistor is recorded as a signal which is proportional to a load current through the power MOSFET, and is fed as a regulating signal to a control device driving the power MOSFET.
A problem when recording the current in that manner is the shunt resistor which is provided in series with the power switch, because that resistor causes power loss. However, such a shunt resistor or series resistor for the inductive load was heretofore the only possibility used to record the current in the inductive load. Besides the increased power loss of the circuit configuration, such a shunt resistor often also had to be provided as a separate component previously, which it was not possible to integrate.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a circuit configuration for pulsed current regulation of inductive loads, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and in which current flowing through an inductive load can be recorded without any, or at least with reduced, power loss.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration for pulsed current regulation of inductive loads, comprising two supply-voltage terminals; a switching device connected in series with the inductive load between the supply-voltage terminals; a measuring device for recording a signal corresponding to a current through the inductive load; and a freewheeling configuration; the freewheeling configuration and the measuring device connected in parallel with the inductive load for measuring current while the switching device is in an open state.
When the switching device is switched on, the current in the inductive load is known to rise. In contrast, when the switching device has been switched off, that is to say when it is in its open state, the current in the freewheeling circuit can continue to flow. The current flowing in the freewheeling circuit when the switching device is switched off is detected in accordance with the invention. This freewheeling current is a measure of the current flowing through the inductive load in the switched-on state and can thus be evaluated for necessary regulating purposes.
The crucial advantage of such current measurement as compared with the otherwise customary shunt resistor is the virtually loss-free possibility of recording the current.
In accordance with another feature of the invention, the freewheeling configuration is produced by using a first diode connected in parallel with the inductive load. In order to record a current flowing through the inductive load, a second diode is connected in parallel with that diode. Cathode connections of the two diodes are connected to one another and are connected to one connection of the integrated load. Anode connections of the two diodes are connected to a different input of an operational amplifier in each case, and a signal which corresponds to the current to be measured is recorded by the measuring device at the output of this operational amplifier.
In accordance with a further feature of the invention, the input of the operational amplifier which is connected to the second diode is connected through a non-reactive resistor to the output of the operational amplifier.
In accordance with an added feature of the invention, the two diodes are produced as switched diodes, e.g. using a MOSFET. Expediently, the switching device is also a MOSFET in this case. The switching device and the switched diodes, that is the three MOSFETs in total, are driven by a driving device which is suitable for this purpose.
In accordance with a concomitant feature of the invention, the two diodes or switched diodes are monolithically integrated in a semiconductor body in order to ensure that the measurement is independent of temperature.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit configuration for pulsed current regulation of inductive loads, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 5612610 (1997-03-01), Borghi et al.
patent: 5925989 (1999-07-01), Blankers
patent: 9105697 (1991-09-01), None
Graf Alfons
Tihanyi Jenoe
Greenberg Laurence A.
Lam Tuan T.
Lerner Herbert L.
Nguyen Hiep
Siemens Aktiengesellschaft
LandOfFree
Circuit configuration for pulsed current regulation of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuit configuration for pulsed current regulation of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit configuration for pulsed current regulation of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449706